In recent years, electronic equipment conforming to digital interface standards such as the DVI (Digital Visual Interface) standard and the HDMI (High-Definition Multimedia Interface) standard has been developed in order to transmit digital video signals (see, for example, Patent Document 1).
Particularly in the HDMI standard, it is possible to multiplex digital sound signals compressed in blanking periods of digital video signals.
When interfaces conforming to the HDMI standard are used, therefore, interfaces for transmitting digital video signals and interfaces for transmitting digital sound signals need not be separately provided.
Conventional digital signal receiving apparatuses conforming to the HDMI standard will be described. FIG. 16 is a block diagram for explaining a digital signal receiving apparatus conforming to the HDMI standard.
FIG. 16 shows a plasma display device as an example of the digital signal receiving apparatus.
A digital signal receiving apparatus 90 includes an HDMI receiver 91, a digital video processing circuit 92, a PDP (Plasma Display Panel) driving circuit 93, an MCU (Microcomputer Unit) 94, and a PDP (Plasma Display Panel) 95.
The digital signal receiving apparatus 90 is provided with an HDMI terminal 90t. A DVD (Digital Versatile Disc) player 70 having an HDMI terminal 70t is connected to the HDMI terminal 90t through an HDMI cable 80.
The DVD player 70 transmits a digital video signal conforming to the HDMI standard to the HDMI receiver 91 in the digital signal receiving apparatus 90 through the HDMI terminal 70t, the HDMI cable 80, and the HDMI terminal 90t in a transmission format conforming to the TMDS (Transmission Minimized Differential Signaling) standard.
The DVD receiver 91 decodes the received digital video signal, and transmits a luminance signal Y, a color difference signal U/V, a horizontal synchronizing signal H, a vertical synchronizing signal V, a data enable signal DE, and a sampling clock signal CLK that conform to ITU (International Telecommunication Union)-R BT.601. The color difference signal U/V has two types of color difference signals U and V alternately multiplexed therein.
The luminance signal Y, the color difference signal U, and the color difference signal V have a color difference format of 4:2:2. The data enable signal DE represents an effective video period in the horizontal direction.
Furthermore, the HDMI receiver 91 detects information (the number of horizontal pixels and the number of vertical scanning lines) relating to the video format of the received digital video signal, and has information relating to the video format stored in its self-contained register.
The MCU 94 reads the information relating to the video format stored in the register of the HDMI receiver 91, and controls the digital video processing circuit 92 on the basis of the information.
The digital video processing circuit 92 recognizes the respective values of the color difference signal U and the color difference signal V for each pixel from the color difference signal U/V in accordance with the control by the MCU 94, and converts the value of the luminance signal Y, the value of the color difference signal U, and the value of the color difference signal V for each pixel, respectively, to the values of primary color signals R, G, and B. The digital video processing circuit 92 feeds to the PDP driving circuit 93 the primary color signals R, G, and B, the horizontal synchronizing signal H, the vertical synchronizing signal V, the data enable signal DE, and the sampling clock signal CLK.
The PDP driving circuit 93 displays a video on a screen of the PDP 95 on the basis of the primary color signals R, G, and B, the horizontal synchronizing signal H, the vertical synchronizing signal V, the data enable signal DE, and the sampling clock signal CLK.
FIG. 17 is a timing chart showing an example of signals transmitted from the HDMI receiver 91 to the digital video processing circuit 92 as shown in FIG. 16.
FIG. 17 shows the color difference signal U/V, the luminance signal Y, the sampling clock signal CLK, the data enable signal DE, the horizontal synchronizing signal H, and the vertical synchronizing signal V.
In this example, suppose a case where the video format of the received digital video signal is other than 525I (60 Hz) and 625I (50 Hz), for example. In this case, one period of the sampling clock signal CLK corresponds to one pixel. One period of the sampling clock signal CLK is hereinafter referred to as one clock. Although two periods of the sampling clock signal CLK correspond to one pixel when the video format is 525I (60 Hz) and 625I (50 Hz), this is not considered in this example.
The color difference signal U/V alternately includes the values of the color difference signal U and the values of the color difference signal V in the period of the sampling clock signal CLK. When the values of the color difference signal U and the values of the color difference signal V are distinguished, the value of the color difference signal U and the value of the color difference signal V are hereinafter respectively referred to as a color difference value U and a color difference value V.
For example, the color difference value U and the color difference value V of a pixel 0 are respectively “U0” and “V0”, and the color difference value U and the color difference value V of a pixel 1 are respectively “U0” and “V0”. The two color difference values U and V common to the two pixels are thus assigned to each of the pixels.
The luminance signal Y includes the values for each pixel in the period of the sampling clock signal CLK. The value of the luminance signal Y is hereinafter referred to as a luminance value Y.
For example, the luminance value Y of the pixel 0 is “Y0”, and the luminance value Y of the pixel 1 is “Y1”. Thus, one luminance value Y is assigned to one pixel. Various types of related information such as information relating to a color difference format, control information, and sound information are multiplexed in a blanking period of the color difference signal U/V and the luminance signal Y.
In FIG. 17, the related information multiplexed in the blanking period of the color difference signal U/V and the luminance signal Y is represented by “val”.
A time period during which the data enable signal DE is at a high level represents an effective video period in the horizontal direction. A time period during which the data enable signal DE is at a low level corresponds to a blanking period. A video composed of a plurality of pixels is displayed on the screen on the basis of the color difference signal U/V and the luminance signal Y in the effective video period.
[Patent Document 1] JP 2006-19809 A